Alloy and process for making same



y o. FEUSSNER ET AL 2,048,648

ALLOY AND PROCESS FOR MAKING SAME Filed June 19, 1954 11v VENTORS 07 TOFEUSSNEE AL F/PED JEDELE ATTORNEYS Patented July '21, 1936 k H ALLOYANDrnocnss Foa G SAME Otto Feussner and Alfred Jedele,

Hanau-on-the-Maln, Germany I Application June 19, 1934, Serial No.731,258. In fislglnm, France, and the Netherlands July 13,

- 15 Claims. for. 148-13) Our present application is a continuation intemperatures, they are tarnish-resisting and expart of our applicationSerial No. 622,568 filed hibit the surprising property of being improvedinthe United States Patent Ofllce' July 14, 1932. by heat treatment tosuch a degree that an in- Our invention relates to alloys which areincrease in hardness of 100% and even more is tended as substitutes forplatinum, for instance easily attained. If, in the alloy, the gold is 5in connection with dental work or for making v mostly or all substitutedby copper, the alloys contacts of electrical apparatus etc. The inwhenheated in air to high temperatures will disvention consists oi? novelalloys of the above incolor in a degree increasing with'the increase indicated class having special desirable properties copper content, butsuch alloys (containing a and also consists in a novel method ofheatrelatively large proportion of copper) respond treating such alloysand thereby improving cermost easily to the process of heat treatment;

tain of their properties. they show a small initial hardness (naturalhard- For the purposes indicated above, binary alloys ness, soft state)and very. great final hardness consisting of palladium and silverhavebeen used after the heat treatment, the increase in hard 1 to somextent, These binary alloys have a ness being quite considerable,exceeding 100% in greater resistance to corrosion and to tarnish manycases. 7 than silver and are also harder than silver. The tin which weincorporate in the above a1- However. even the hardest binarypaliadiumloys as a special hardener should be used in prosilver alloy(with equal parts of silver and palportions not less than .5%' and notmore than ladium) has a hardness only about twice the 5%. In some casesthe metals used as the basis hardness of these two metals, which arevery of the alloy may contain small proportions of soft. The Brinellhardness of either palladium metals of the plat num 811311903181 a P orsilver alone is about 40 kilograms per square ladium, for instanceruthenium, rhodium, or millimeter and an alloy made of equal parts ofplatinum, up to 8%. or up to 3% of these other UNITED STATES PATENTOFFICE silver and palladium has a Brinell hardness of metals of theplatinum group may be added inabout 80 kilograms per square millimeter.These tentionally; wi ou defeating the advantages of binarypalladium-silver alloys can not be imthe present invention. The presenceoi" these proved by heat treatment. If a ternary alloy other metals ofthe P g oup i increase is made by adding gold to the palladium and thenatural or initial hardness of these alloys 3 silver, the resistance tocorrosion, to mechanical and will also increase the final hardness which3 action and to tarnish becomes very high but is obtained by thesubsequent heat treatment. heat treatment does not improve these ternaryIn some cases it is desirable to lower the meltalloys any more than thebinary alloys first ing point oi! the resulting alloys and to increasementioned. If a ternary alloy is produced by their liquidity. We havefound that when this adding copper to palladium and silver, suchallowering of the m t po a d increase in loy, which istarnish-resisting, will indeed show liquidity are desired, the additionof phosphorus some improvement in hardness when heat in proportions notless than 5% and not more treated. but such improvement is only veryslight. than 4% will accomplish this result in connec- 40 If instead ofcopper alone, copper and gold are tion with the above alloys containingtin as a added to palladium and silver, the resulting alhardener. Wehave found that the addition of loys are of the same characteristics asthe terphosphorus (preferably in the form of red phosnarypalladium-silver-copper alloys; that is to phorus powder or phosphoruscopper) generally say, heat treatment. or aging", will improvedecreasesthe melting point of the alloys by about their hardness butslightly. 150 C. These alloys containing phosphorus 45 By systematicinvestigations we. have found have a very low viscosity and flow easilyand freely that considerable improvement is obtained when into anycavity. They are especially suitable tin is added in making alloyscontaining palfor casting purposes, for instance in dental work. ladium,silver, and another'(fourth) constituent These phosphorus-containingalloys would be which consists either of copper or of gold or cast inthe shape required for the dental work of both of these metals. In otherwords, the new in each particular case. These castings can be 5 alloyscontain at least four metals, three of which adjusted or altered withinslight limits, for inare palladium, silver and tin. These new alloysstance by filing, but can not be hammered or (if their fourthconstituent consists of gold alone rolled. These phosphorus-containingcastings u or of goldwith a small proportion of copper) can be improvedby heat treatment in the same when heated in air do not discolor even athigh I way as the tin-containing alloys of our invention containing nophosphorus, and with the same I 7 degree of increase in hardness.

hour at temperatures from 700 to 1000 C. and

are then quenched in water. The alloys are then in a soft condition,that is to say, they have only their natural hardness. .In thiscondition (if 7 they contain no phosphorus) the alloys can be easilyworked and shaped into sheets, wires or any other form that may bedesired for the particular use for which they are intended. From thissoft, condition, the alloys are improved, and

particularly increased in hardness, by a heating or aging treatmentconducted at temperatures ranging from iOO to 700 C. We have found thatthe structure of'the new alloys is altered considerably during theprogress of, such heat treatment. When the alloys are in the soft stateresulting ifrom annealing at 1000' C. and subsequent quenching, :theirstructure is one with large crystals having very distinct boundaries. Ifthe alloys are then re-annealed or aged for a certain length of time.depending on the temperature employed for such ag'in'g, deposits orsegregations will appear between the crystal boundaries, and itis thesedeposits or segregations which cause the increase in hardness. The lowerthis temperature is, the greater will be the length of time required tobring about these segregations: with a temperature of 600 C. about onehour will be sumcient, while with a temperatureof 500 0., about threehours will be required to produce these segregations. If there-annealing or aging is then continued, especially at the relativelyhigh temperature of 650 C., the boundaries of the crystals .disappeargradually and have vanished completely after a sufficient lapse of time,say about fourteenhours. The alloys are then of a very homogeneousstructure and will exhibit a very minute-and uniform grain when pickled.The higher the temperature that is employed, (the more closely itapproaches 700 C.) the shorter will be the 'time required to effect thehomogenization of the alloy. It is well known that the size of the grainboundaries determines to a large extent the mechanical properties of anyalloy; alloys with large grains are mechanically weaker than alloys withvery minute grains. A heat treatment of an alloy which diminishes thesize of the grains to the extent indicated above therefore transformsthe alloy into a very valuable condition. We desire it to be understood,however, that evena relativelyshort aging treatment (say of one hour)will increase thehardness of the alloys considerably, but ductility ofthe alloys (as measured by resistance to repeated bending) is not fullydeveloped by such short treatment. In all cases where a very even andsmooth grain is required, the longer heat treatment as referred to abovewill be employed to produce a very homogeneoushard product ofincreasedductility.

The preferred proportions employed by us are as follows:

- Per cent Copper and/or gold to Palladium -to50 Silver 72 to Tin .5 to5 When greater liquidity and the lowering of the melting point aredesired as explained above,we

'ployed in ,these cases:

add to the above from no its: phosphorus. It will be understood that inaddition to the ingredients Just mentioned. the alloys may contain smallproportions of metals of the platinum group other than palladium, forinstance ruthenium, rhodium," or platinum.

- The following examples indicate deflnit'e proportions which we havefound to be particularly suitable in some cases and also set forth theparticular heat treatment which we have em- Ezomple 1 An alloyconsisting of of palladium, 50% of silver, 6% of gold, 4% of tin wasproduced by melting these ingredients .and cast to sheet bar. The barwas then annealed for one hour at 1000" C. and quenched in water therebybringing it into the soft state. The bar was then rolled into a sheet ofa thickness of 0.3 millimeters. The rolling operationwas generallyconducted in a number of successive passes, and between each two passesthe metal was subjected to an intermediate annealing at 1000 C. andquenched in water before the next rolling pass. After completion of therolling operation the 'sheet was again annealed at 1000 C. and thenquenched in water. The metal was then in a relatively soft state, asindicated by the fact that a strip of such sheet would breah after beingbent 5000 times. Thereupon this soft sheet was aged for fourteen hoursat 650 6., and its ductility and other propertieswere so much improvedby'this aging treatment that it sustained 15000 bendings beforebreaking. 7

Example 2 A series of alloys were prepared each containing 2% 01' goldand 3% of tin, with the percentage of copper varying from 4 to 7%, thatof palladium from 20 to 40% and that of silver from 71 to 48%.

kilograms per square millimeter as indicated in i Table I below. Thenfollowed a re-annealing or aging for'one hour at 800 '0. followed byslow cooling whereby. the hardness of the alloy in the aged conditionwas increased considerably, ranging from 180 to 2'15 kilograms persquare millimeter as likewise indicated in the following table;

Table! Soft v a d on Pd a; v

v .Kllognmpc 4 20 'n m is) s an '10 no an s so no. 145 as s .40 so, noan o 40 40 120 an 1 so as m m The increase .in by the palladium contentis more than 40%. but is relatively small in such cases. For instance,when the alloy (with 2% gold and 8% tin) contains 5% 7 treatment of ourinvention is observed even when of copper, 50% of palladium and 40% ofsilver, it"

has a Brinell hardness of kilograms per square millimeter after theannealing treatment at 1000 C. for one-half hour followed by quenchingin water (soft state), which hardness is increased to 135 kilograms persquare millimeter by the aging treatment described above (annealing forone hour at 600 C. and slow cooling).

. We may decrease the copper content to 3% in the case of alloyscontaining 2% of gold and 3% tin. In such cases, however, the increasein hardness obtained by the aging treatment is considerable only whenthe palladium content of the alloy ranges from 30 to at palladiumpercentages below 30 and above 40, the increase in hardness obtained bythe aging treatment is relatively slight as will be seen by thefollowing table? It will be understood ment and the subsequent agingtreatment in connection with alloys of Table II may be the same asdescribed in connection with the alloys of Table 1, that is to say;annealing at 1000 C. for one'hali hour followed by quenching in waterand reannealing or aging for one hour at 600 C. followed by slowcooling.

The addition of phosphorus in the proportion indicated (from .5 to 4%)is made to any one oi the alloys specified above whenever it is desiredto reduce the melting point and the viscosity of the alloy whileincreasing its hardness beyond its natural hardness. The annealing,quenching and aging treatment may be exactly the same for a particularalloy whether or not phosphorus is added thereto. That is to say, if thealloy set forth in Example 1 is changed by simply adding phosphorusthereto within the range indicated, the treatment of such alloy would beexactly the same as described in connection with Example 1. The sameremark will apply to the other examples. The addition of phosphoruslowers the melting point of the alloy very considerably and brings itdown to the level of the melting point of gold or of gold alloys; thisis a considerable advantage in certain cases, particularly for dentists.

The considerable and advantageous alterations in the structure of thematerial which the heat treatment according to our invention produces,are shown very clearly in the accompanying drawings which arereproductions of microphotographs taken from an alloy of the compositionof Example treated according to our invention. These microphotographswere taken with an enlargement of 135 diameters. Fig. 1 shows thestructure after annealing for one hour at 1000" C. and quenching; Fig. 2shows the same alloy after re-annealing or aging at 600 C. for one hour;Fig. 3 shows the condition of the alloy after an aging treatment ofseven hours at the temperature of 650 C., (instead of one hour at 600C.) and Fig. 4 shows the same alloy after an aging treatment of fourteenhours at 650 C.

Where in the appended claims we use the expression "substantiallyconsisting of about", we desire this to be interpreted as meaning thatthe alloys may'also contain other metals of the platthat the annealingtreatinum group in minor amounts, and such substances, as for instancephosphorus, which do not materially change the properties of the alloysto be hardened by heat treatment, but do improve the alloys as to theirnatural hardness, melting point, liquidity, etc. Again, where in the ap?pended claims we use the expression from 5 to 10% of a constituentselected from the group consisting of gold and copper", we desire thisto be interpreted in accordance with our specification, where we havestated that the preferred proportions employed by us include 5 to 10% ofcopper and/or gold; in other words, this 5 to 10% constituent mayconsist either of copper alone, or of gold alone, or of copper and goldtogether.

Various modifications may be made without departing from the nature 01'our invention defined in the appended claims.

We claim:

1. An age hardening alloy substantially consisting of about 20 to 50% ofpalladium, 72 to 30% of silver, from 5 to 10% of a constituent selectedfrom the group consisting of gold and copper, and 0.5 to 5% of tin.

2. An age hardening alloy substantially consisting of about 20 to 40% ofpalladium, '71 to 48% of silver, 2% of gold, 4 to 7% of copper, and 3%of tin.

3. An age hardening alloy substantially consisting of about 40% ofpalladium, 48% of silver, 2% of gold, 7% of copper, and 3% of tin.

4. An age hardening alloy substantially consisting of about 20 to 50% ofpalladium, 72 to 42% of silver, 2% of gold, 3% of.copper, and 3% of tin.

5. A dental element in the form of a member cast in the shape requiredfor the dental work in the particular case, said cast member having thecharacter of an alloy set forth in claim 1.

6. A dental element in the form of a member cast in the shape requiredfor the dental work in the particular case, said cast member having thecharacter oi an alloy set forth in claim 1, in which the melting pointof the liquid alloy is lowered and the liquidity increased by theaddition of not less than 0.5% and not more than 4% phosphorus.

7. An alloy hardened by heat treatment and consisting substantially ofabout 20 to 50% of palladium, 72 to 30% of silver, from 5 to 10% of aconstituent selected from the group consisting of gold and copper, and0.5 to 5% of tin.

8. A dental element in the form of a member cast in the shape requiredfor the dental work in the particular case, said cast member having thecharacter of an alloy set'iorth in claim 1 and being hardened by heattreatment.

9. A dental element in the form of a member cast in the shape requiredfor the dental work in the particular case, said cast member having thecharacter of an alloy set forth in claim 1, in which the melting pointof the liquid alloy is loweredand the liquidity increased by theaddition of not less than 0.5% and not more than 4% of phosphorus, saiddental element being hardened by heat treatment.

10. The process which consists in subjecting an alloy substantiallyconsisting of about 20 to 50% of palladium, 72 to 30% of silver, from 5to 10% of a constituent selected from the group consisting of gold andcopper, and 0.5 to 5% of tin, to an annealing treatment at a temperatureof from 700 to about 1000 C. and then quickly cooling the alloy thusheated, and thereupon aging it by heating to a temperature ranging fromabout 400 to 700 C.

alloy substantially consisting of about 40% of palladium, 48% ofsilver,'2% of gold, 7% of copper, 3% of tin, to an annealing treatmentat a alloy substantially consisting or about 20 to 50% of palladium, 72to 30% of silver, from 5 to of a" constituent selected from the groupconsisting ofgold and copper, and .5 to 5% of tin, casting I such alloyin the shape required for the dental work in the particular case, thenheating such casting to a temperature within the range of about 700 to1000 C., quickly cooling the casting, and thereupon aging it by heatingto a temperature ranging from about 400 to 700 '3.

15. The process of producing a dental element which consists inproducing'in the soft state, an i alloy substantially consisting ofabout to 50%; v of palladium, 72 to of silver, from 5 to 10% or aconstituent selected from the group consistl5 ing of gold and copper, .5to 5% of tin, and not temperature oi. from 700 to about 1000 C/and thenquickly cooling the alloy thus heated, and thereupon aging it by heatingto a temperature ranging from about 400 to 700 C.

13; The process which consists inv subjecting an alloy substantiallyconsisting of about 20 to of palladium, '72 to 42% of silver, 2% ofgold, 3% of copper, and 3% of tin, to an annealing treatment at atemperature or from 700 to about 1000 C. and then quickly cooling thealloy thus heated, and thereupon aging it by heating to a temperatureranging from about 400 to 700 C.

14. The process of producing a dental element which consists inproducing in the soit'state, an

less than .5 and not more than 4% of phosphorus, casting such alloy inthe shape required for the dental work in the particular case, thenheating such casting to a temperature within 20 the range of about 700to 1000 C., quickly cooling the casting, and thereupon aging it byheating to a temperature ranging from about 400 to 700 C.

ALFRED JEDELE.

